The role of the lymphatic system in the absorption and distribution of antitumor agents (CCNU, methyl-CCNU, guanazole, dibromomannitol, diethylstibestrol, prednisolone, dexamethasone, 6-mercaptopurin, cytosine arabinoside, vincristine, cyclophosphamide, adriamycin, daunomycin, actinomycin D and o,p-DDD) and other model substances (serum albumin, latex microspheres and liposomes) administered to rats by oral, iv or ip routes is under investigation. The importance to lymphatic absorption of the molecular weight and lipid solubility of the agents and the vehicle or formulation in which they are given is also being evaluated. Studies on liposomal encapsulation of hexamethylmelamine, pentamethylmelamine and adriamycin are in progress. The lymphatic absorption and physiologic disposition of liposome-encapsulated adriamycin administered by ip injection to rats is being evaluated and compared with that of free adriamycin. Efforts are underway to develop a reproducible model system in rodents for tumor metastasis via lymphatic channels, so that the therapeutic advantage of treating such tumors with antitumor agents selectively taken up by lymphatics can be tested.